Password Spraying

People don't always choose strong passwords, neither do IT people for temporary accounts. Spraying passwords against all found user accounts is effective for getting access to the domain.

Configuring

Prerequisite

Username Enumeration

Configuring

1. To implement the attack we need to set a weak password for some of the users we created and enumerated in the previous step. The easiest way is by using the net user command in the terminal. To change the password for john to Welcome2022! and chris to Summer2022! execute the following commands on DC02:

net user john Welcome2022! /domain
net user chris Summer2022! /domain

Attacking

How it works

Password spraying is a type of brute force attack. An attacker will try a default password against a list of usernames. For example, an attacker uses the password Welcome2022! against many different accounts to avoid account lockout that would normally occur when brute-forcing a single account with many passwords.

A old habit what a lot of companies enforce is the requirement to change passwords every 30, 60 or 90 days. Which results in people changing their password often, forgetting it and eventually choosing a easy guessable password. Another habbit is adding a increment to the same password or using months/seasons. Which means we can easily create a password list of common passwords and things people would choose using following formats:

• season+year+! (Summer2022!)

• month+year+! (March2022!)

• companyname+year+! (Amsterdambank2022!)

• city+! (Amsterdam!)

• etc.

Tools

• Kerbrute

• Spray

• Crackmapexec

• Domainpasswordspray

• Rubeus

Executing the attack

Spraying a single password

To spray a single password from our kali machine we will use kerbrute again. But this time we will use the passwordspray functionality. We will spray the password Welcome2022! against all the users we enumerated earlier.

./kerbrute_linux_amd64 passwordspray -d amsterdam.bank.local --dc 10.0.0.3 ~/adlab/users.txt 'Welcome2022!'

It is recommended to not spray more then one password every 30 minutes to prevent locking out accounts. We don't have access to the domain yet and can't retrieve the current passwordpolicy.

Spraying a small list of passwords

1. To spray a list of passwords we can use Spray. First create a passwords.txt file and copy the following passwords:

Spring2022!
Winter2022!
Autumn2022!
Summer2022!
Welcome2022!
Bank2022!
AmsterdamBank2022!

2. Since we don't want to lock any accounts we will try one password every 31 minutes by using the following command:

bash spray.sh smb 10.0.0.3 ~/adlab/users.txt ~/adlab/passwords.txt 1 31 passwordspray.txt

For demonstration purposed we used 1 minute in the screenshot.

Defending

Recommendations

• Implement a strong password policy:

Strong Password Policy

Detection

References

GitHub - ropnop/kerbrute: A tool to perform Kerberos pre-auth bruteforcingGitHub

GitHub - Greenwolf/Spray: A Password Spraying tool for Active Directory Credentials by Jacob Wilkin(Greenwolf)GitHub

GitHub - byt3bl33d3r/CrackMapExec: A swiss army knife for pentesting networksGitHub

GitHub - dafthack/DomainPasswordSpray: DomainPasswordSpray is a tool written in PowerShell to perform a password spray attack against users of a domain. By default it will automatically generate the userlist from the domain. BE VERY CAREFUL NOT TO LOCKOUT ACCOUNTS!GitHub